Found one reference to it being bolted in 1988: https://www.planetmountain.com/en/news/interviews/alexander-megos-interview-after-his-ascent-of-biographie-at-ceuse.html
And more references to 1989, or even 1989–90, e.g: https://www.thecrag.com/es/escalar/france/ceuse/route/15807193
Does anyone have some solid info on this? Maybe a guidebook?
I think the 1988 we currently have came from the planetmountain article, so I don't have a better source than that.
Now have a copy of the guide on it's way :D Will let you know if there's a date in there.
Just need a wealthy patron or two to sponsor the fact finding mission. In the name of historic accuracy!
Guidebook has arrived, it has the details as B.Drouillard, JC.Lafaille 1988.